Leisure time after school is crucial for a proper development of young individuals. However, factoring the role of various leisure activities in explaining their well-being at school and school grades is not well understood. The conducted research aimed at addressing this gap by examining 182 adolescents, aged between 15 and 18. As a conclusion, it was found that both well-being at school and academic performance were positively influenced by time spent with parents but negatively affected by time spent playing video games. Excessive participation in organized leisure activities was negatively related to relationships with peers and teachers. Some passive activities that promoted school skills, such as painting, drawing, and reading, positively predicted academic performance of adolescents. These findings highlight the importance of free time after school for adolescents’ well-being in an educational context, as they also have implications for the social policy.